1. Field of the Invention
The present invention relates to a power supply control system comprising a plurality of power supply circuits which supply powers to loads driven at a plurality of voltages, at voltages corresponding respectively to the plurality of voltages, and to a storage device comprising a disk drive unit for storing input data, and a cache memory which temporarily keeps the data stored in the disk drive unit.
2. Description of the Related Art
In the prior art, a power sequence detecting unit has been proposed with the aim of shortening the time required until the cause of an operational fault can be identified, in cases where an operational fault occurs in the power supply section, due to an error in the power supply sequence that cannot be fully detected. In such as device, the power supply control section controls the start-up of the power supply output of three power supply units, for example, and at the start-up timing, the output power voltages of the respectively power supply units are compared with a previously determined prescribed value, and logic signals based on these comparisons are output by respective comparators and the NOR circuit. In accordance with the output of these logic signals, a distinction can be made between a normal and error state of the power output of the three power supply units. Therefore, if there is an error in the power supply sequence, the suspect power supply unit can be identified, and the source of an operational fault caused by an error in the power supply sequence can be detected at an early stage (see, for example, Japanese Patent Laid-open No. 2000-188829).
Conventionally, almost all LSIs (large-scale integrated circuits) used in electronic devices have required a 5V DC (direct current), but in recent years, with miniauthorization of the manufacturing process for LSIs, there have appeared LSIs requiring voltages of 3.3V DC, 2.5V DC, 1.8V DC, 1.5V DC, or the like, for example, other than 5V DC. Furthermore, with miniauthorization in the manufacturing process for LSIs, in many LSIs, the DC voltage applied to each chip inside the LSI and the DC voltage applied to the I/O (input/output) section of the LSI are different, and in an increasing number of LSIs, the power input sequence to each LSI is specified, in order to prevent breakdown of the element. In view of this technological background, power supply sequence circuits which are conventionally constituted by discrete components are becoming increasingly complex in structure, in order to respond to the various demands brought by miniaturization of the LSI manufacturing process as described above.
However, the aforementioned power supply control LSI is only provided with a function for performing simple sequence control, and although no problem will arise when the power supply circuit section subject to control is operating in a normal state, if the power supply circuit section declines into an error state, for some reason or other, then the voltage value immediately prior to entering this error state is unknown, and therefore, it is difficult to carry out fault analysis of the power supply circuit section by means of the power supply control LSI described above.
Furthermore, in a storage system comprising a disk array unit constituted by a plurality of storage devices arranged in an array configuration, such as a RAID (Redundant Array of Independent Inexpensive Disks), for example, the process for halting the drive power is complex and varied depending on the type of incident occurring in the system, and hence more detailed control is required and a power supply control LSI such as that described above is not capable of providing a suitable response.